The present invention relates generally to a motor, a method of manufacturing the motor and a rotary apparatus equipped with the motor and, more particularly, to a motor which can be assembled with accuracy and which can be manufactured easily and at low cost, and to a method of manufacturing the motor and to a rotary apparatus equipped with the motor.
Conventionally, a motor as shown in FIG. 6 has been used for a rotary apparatus, such as a rotary polygon mirror apparatus such as a laser beam printer and an HDD drive.
The motor of FIG. 6 has a base 110 having a fit portion 11a in the form of an annular projection, a hub shaft 130 having a shaft 131 extending from a center of a disk-formed hub 132, and a bearing ring 152 secured to a lower end of the shaft 131.
The bearing ring 152 is inserted in the fit portion 11a so that the hub shaft 130 can be rotatably supported on the base 110.
A stator coil 140 is fixed on an outer periphery of the fit portion 110a. 
An annular portion 133 extends downward from a peripheral edge of the hub shaft 130. The annular portion 133 has a rotor magnet 160 fixed on an inner peripheral wall of the annular portion 133.
The stator coil 140 forms a rotating magnetic field so that the rotor magnet 160 can be excited to rotate the hub shaft 130.
The base 110 is fixed on a chassis of a main body apparatus, such as a printer or HDD drive.
The motor described above is required to operate with reduced vibration and noise during rotative drive because of its usual use in a calm place, such as an office. Particularly, an HDD drive is required to provide accurate position data reading by a magnetic head, due to recent density increase of hard disks. Thus, there is a need to reduce vibrations as much as possible from this viewpoint.
Furthermore, the stator magnet of the stator coil 140 or the like and the rotor magnet 160 if not aligned in their magnetic centers require increased power consumption to obtain required rotation. Furthermore, this would cause wow and flutter in rotation leading to a cause of vibrational noise. Consequently, there is a necessity of assembling the parts with accuracy to correctly position between the stator magnet and the rotor magnet 160.
Meanwhile, for a motor for use in an HDD drive, the distance should be kept at a predetermined length between a hard disk to be loaded and a magnetic head. Consequently, it is required to exactly position in height of the hub in order for supporting a hard disk with reference to the base.
In the meanwhile, in the conventional motor as shown in FIG. 6, the stator coil 140 is a most serious vibration source. Because the stator coil 140 is mounted on the base 110, vibration on the stator coil 140 is directly conveyed to the base 110. The vibration is transmitted through the base 110 onto a main body apparatus, such as a printer or HDD drive, causing noise to the outside. In this manner, the prior art motor involves a problem that vibration is directly conveyed to the outside thus resulting in noise.
Also, in the above motor, the base 110 is fixed with a stator coil 140 and the hub shaft 130 with a rotor magnet 160. Consequently, the adjustment in height of the base 110 and the hub shaft 130 also determines a positional relationship between the stator coil 140 and the rotor magnet 160. Due to this, the stator coil 140 and the rotor magnet 160 are almost determined in their magnetic center position during forming the parts. It is accordingly impossible during assembling to adjust an error of mounting the stator coil 140 to the base 110 or an error of attaching the rotor magnet 160 to the hub shaft 130. Thus, in the above motor, there is a problem that it is difficult to manufacture an precise product with respective positional relationships correctly kept between the base 110 and the hub shaft 130 and between the stator coil 140 and the rotor magnet 160.
Furthermore, in the above motor the base 110 is fixed with the stator coil 140 and the hub shaft 130 is fixed with the rotor magnet. The motor characteristics (electrical and vibration characteristics, etc.) can be measured first on a final product after assembling the hub shaft 130 on the base 110. When poor assembly is detected, the product must be scrapped in its entirety, including the expensive base, resulting in a reduction of efficiency and increase in cost.
The present invention has been made in order to solve the above problems in the conventional art. It is an object of the present invention to provide a motor which operates with reduced noise during driving and which can be manufactured easily, efficiently and inexpensively with accuracy, and to a method of manufacturing the motor and a rotary apparatus equipped with the motor.
The motor of the present invention comprises; a columnar support member; a base formed separate from the support member and having a fit portion in which the support member at one end is fitted; a rotor member rotatably supported coaxially to the support member; a regulating means for regulating a position of the rotor member in an axial direction relative to the support member; a magnet fixed on one of the support member and the rotor member; and a plurality of electromagnets fixed facable to the magnets on the other of said support member and the rotor member to form a rotating magnetic field so that the magnet is excited to rotate the rotor member. This achieves the above object.
In the motor of the invention, the support member is fixed with one of the magnet and the electromagnet, and this support member is formed as a separate member from the base. Due to this, it is possible during driving to avoid transmission, directly from the support member to the base, of vibration caused by attracting and repelling forces due to a magnetic field formed by the stator coil and the magnet or vibration due to deviation in a magnetic field center. Accordingly, noise during driving is reduced.
In the motor of the invention, the magnet is fixed on one of the support member and the rotor member and the electromagnets are fixed on the other, and the support member and rotor member are formed separately from the base. The axial position of the support member relative to the base is determined by a positional relationship between the support member and the base. Also, the axial positions of the magnet and electromagnets are determined by a positional relationship between the support member and the rotor member, regardless of the base. Due to this, it is possible to independently conduct, without mutual affection, axial aligning between the base and the support member and between the electromagnets and the magnet. Accordingly, the motor of the invention can be manufactured easily and with favorable assembling accuracy.
Also, after fixing the electromagnets and magnet on the rotor member and support member, it is possible to align between the base and the rotor member and between the electromagnets and the magnet. Accordingly, it is possible to rectify an error occurring upon fixing the electromagnet and magnet on the rotor member and support member or an error caused in forming the parts. Therefore, the motor of the invention can be manufactured easily and with favored assembling accuracy.
In this manner, manufacture with favorable accuracy and accurate alignment between the electromagnets and the magnet are possible to conduct, making possible to avoid noise to be caused due to deviation in magnetic field center.
In the motor of the invention, the magnet is fixed on one of the support member and the rotor member, and the electromagnets are fixed on the other, wherein the support member and the rotor member are formed separately from the base. Accordingly, it is possible to energize the coil and conduct a test as a motor, such as measurement of electrical and vibration characteristics after fixing the magnet and electromagnets on the support member and rotor member but before fixing the support member on the base. Only an acceptable assembly can be fit with the base to provide a final product. Accordingly, it is possible to eliminate a useless process of fitting an unacceptable assembly to the base, eliminating useless use of bases. Thus, unintentional increase of cost can be avoided.
In a motor of the invention, the support member is in a sleeve form with a hollow space to have one end communicating the hollow space to an outside and the other end fitted in the fit portion; the rotor member having a shaft portion inserted in the hollow space of the support member from a side of the one end, an extension portion radially extended from the shaft portion to an outer side of the one end of the support member, and an annular portion extended from an peripheral edge of the extension portion toward the shaft portion; the magnet being fixed on one of an outer peripheral wall of the support member and an inner peripheral wall of the annular portion; and the electromagnets being fixed on the other of the outer peripheral wall of the support member and the inner peripheral wall of the annular portion.
The regulating means comprises a bearing ring coaxially fixed on a tip of the shaft portion and an engaging ring fixed on the sleeve to abut against the bearing ring on a side of the extension portion rather than the bearing ring.
A motor according to the invention can be manufactured by a motor manufacturing method including: a first process of fixing the magnet on any one of the support member and the rotor member; a second process of fixing the electromagnets on the other of the support member and the rotor member; a third process of forming, after the first and second processes, a motor unit that the rotor member is regulated in axial position relative to the support member by the regulating means into a state that a magnetic center of the magnet and a magnetic center of the electromagnets are aligned in axial position; and
a fourth process of fitting and fixing, after the third process, the support member in the fit portion of the base.
A rotary apparatus according to the invention has a motor of the invention.
The rotary apparatus of the invention thus provided with a motor of the invention is reduced in noise and can be accurately manufactured easily and efficiently and at low cost.